Phototherapy relates to treatment of biological tissues, preferably skin tissues, using visible, ultraviolet, and/or infrared lights. The light treatment may be applied solely for sterilization, bio-modulation, and photo-rejuvenation. Alternatively, the treatment may be used in combination with certain photo-sensitive drugs or nutrition supplements. In comparison with laser surgery, the light intensity employed in phototherapy is much lower. Thus the light sources used in phototherapy are not limited to lasers but may include light emitting diodes (LEDs) and/or certain lamps as well. Typical applications of phototherapy include wound healing, pressure ulcer treatment, psoriasis reduction, skin rejuvenation, etc.
Certain abnormal skin conditions, such as pressure ulcer, develop from the subcutaneous tissue and are hardly observable from the surface layer of the skin in their early stages. This places a barrier for using phototherapy to treat these abnormal skin conditions when they are still in their early phases, when the phototherapy is most effective. In addition, phototherapy generally causes only subtle changes to the surface layer of the tissue and in some cases its impact only occurs in the inner layer of the tissue. This makes it difficult to evaluate the effectiveness of the phototherapy procedure. Therefore, it is desirous to overcome the above barriers with improved devices.
Ultrasonic imaging techniques are known to be employed in laser surgery apparatus.
In U.S. Pat. No. 5,377,683 to Barken, a catheter having an ultrasound transducer and a plurality of optical fibers for conveying laser light from an external laser source to the tip of the catheter is described. The ultrasound and the laser are connected to a computer system which is used to display ultrasonic images of internal tissue areas within the patient's body and control firing of the laser in response to delimiting input from the physician.
In U.S. Pat. No. 5,967,984 to Chu et al., a catheter having a catheter body of extended length for insertion within a body of a living being is described. The catheter includes an ultrasound imaging device disposed within a distal portion of the catheter body to display a real-time image of tissue surrounding the distal portion of the catheter. The catheter further includes a cutting element, e.g., an electrode wire or a laser fiber. The ultrasound imaging device is positioned relative to the cutting element such that the real-time image produced by the ultrasound imaging system can include the cutting element in relation to the tissue.
In U.S. Pat. No. 6,135,994 to Chernoff, a cosmetic surgical method is described. The method comprises successively orienting an ultrasound transmitter to transmit ultrasound from multiple locations adjacent the skin surface and at each of the multiple locations transmitting ultrasound, generating a time base, receiving ultrasound echoes, and determining from the time between transmission and reception the depth beneath the skin of tissue to be treated. The depths of the tissue at the multiple locations are stored in a memory associated with a programmable machine. The laser is successively targeted on each of the multiple locations, and at each of the multiple locations the depth of the tissue to be treated beneath that location is retrieved from the memory. The retrieved depth of the tissue to be treated beneath that location determines a laser excitation power that will achieve treatment of the tissue at the retrieved depth. The laser is excited at the determined excitation power.
As can be seen, the previously disclosed applications are limited to utilizing the ultrasonic image as a reference for laser ablation and/or coagulation. The application of ultrasonic imaging technique for the non-invasive phototherapy procedure is still a new territory to explore, where a two-dimensional (2-D) or a three-dimensional (3-D) ultrasonic image of the target tissue with much higher spatial resolution is required.